Incandescent-lamp signal.



E. B. PARSONS. INCANDESCENT LAMP SIGNAL.

APPLICATION FILED JUNE 10. l9l5.

Patented Aug. 27, 1918.

l/VVE/VTOI? BY X Z, ATTORNEY Emma s ES PATENT OFFICE.

ELI BURTON PARSONS, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAY SIGNAL COMPANY, OF GATES, NEW YORK, A CORPORATION OF NEW YORK.

INCANDESCENT-LAMP SIGNAL.

Specification of Letters Patent.

Patented Aug. 27, 1918.

Application filed June 10, 1915. Serial No. 33,348.

' way service, and has for its main object to provide a signal of this class which, while having but one lamp arranged behind either a single or compound lens, is no more liable to dangerous extinguishment and has greater light efliciency than the ordinary signal having two lamps behind a lens structure.

he invention comprises a lamp signal including a vacuous bulb containing an incandescent light source having duplex or plural filament portions, one havin longer life than the other, and both' disposed quite symmetrically about the focal center of the lens structure and preferably in substantially the same general horizontal plane, whereby the light rays are most efficiently refracted by the lens or lenses to assure maximum lighting effect of the signal, and whereby should one filament portion burn out Or otherwise break, the other filament portion will persist or remain intact to further and temporarily give a more dim but still effective light and thus avoid accidents pending substitution of a new and perfect lamp bulb structure.

Other objects and advantages will appear as the description of the invention progresses, and the novel features of the invention will be particularly pointed out in the appended claims.

Reference is made to the accompanying' drawings forming part of this specification, and 1n which Figure 1 is a vertical sectional side view of a two-light railway signal showing the general arrangement of its two lamp bulbs of different form respectively having duplex or plural incandescing filaments supported quite symmetrically about the focal centers of the two respectlve red and green lenses of the signal. Fig. 2 is an enlarged broken side view of the upper lamp bulb with its duplex filament, and Fig. 3 is an enlarged broken side view of the lower lamp bulb with its duplex filament. The numeral 1, indicates a suitable ligh signal casing which as shown has two lamp compartments 2, 3, respectively having front red and green lenses 4, 5, the focal centers of which are located on the dot-dash lines aa in the drawing. Quite symmetrically about a point at the focal centers of the lenses are sustained the filaments of two incandescent electric lamps 6, 7. The lamps may be supported in the casing by screws 8, passed through flanges of the lamp sockets 9, or

in any other preferred manner sustaining the lamp filaments as aforesaid substantially about the focal centers of the lenses. The lamp bulbs may have any form, the bulb of lamp 6 being lobular, and the bulb of lamp 7, being e ongated in order to provide suflicient vertical interior space to freely accommodate the modified duplex or plural filament shown therein. The threaded lamp base 10, which screws into the socket 9, has the usual contact terminals 11, 12, with which are connected the respective positive and negative current conductors 13, 14, which are embedded-and sealed within the glass support or pillar 15, to the reduced extremity of which are held any suitable supports 16, 17, for the two filaments 18, 19, of lamp 6, and the two filaments 20, 21, of lamp 7. In lamp 6, both ends of each filament 18, 19,-are directly connected to the extremities of the conductors 13, 14, and these filaments are both set in substantially Similar general horizontal plane, but in the modified lamp 7, the duplex or plural filaments 20, 21, are shown sustained one above and only slightly separated from the other and in substantially similar general vertical plane. This filament arrangement in lamp 7, necessitates branching of the two main conductors to provide two branches 22, 23, leading from respective main conductors 13, 14, to opposite ends of the upper filament 20, and two other branches 24, 25, leading from respective main conductors 13, 14, to opposite ends of the lower filament 21. With this arrangement of filaments and conductors the duplex or plural filaments 18, 19, of lamp 6, or the duplex or plural filaments 20, 21, of lamp7, will be raised to illuminating incandescence when the lighting circuit is closed.

The duplex filaments 18, 19, of lamp 6, and the duplex filaments 20, 21, of lamp 7, are so proportioned or constructed relatively to each other that either filament 18, 19, of

lamp 6, or either filament 20, or 21, of lamp 7, shall have longer life than the other. This relative longevity of one of each pair of duplex lamp filaments may be attained in any suitable or preferred. manner, as for instance by making one of each pair of fila-. ments longer than the other thereby obtaining greater resistance of the longer filament and giving it longer life, or by giving one of each pair of filaments a lower current density to insure some days longer life to the filament having lower current density, or by designing one of each pair of filaments for higher voltage than the other to assure longer life of the higher voltage filamental portion. With the above described relative construction and arrangement of the two filaments of each lamp it is obvious that when both filaments are normally incandescent they will give maximum candle power light at or near the focal center of the signal lens 4, or 5, thereby assuring maximum efiiciency of the signal lamp, and

' when one of the tivo lamp filaments breaks,

the other filament will persist to temporarily give a more dim but still effective danger or clear light signal, and this dimness of itself will be ample Warning to the attendant or trainmen that the lamp needs renewal, and another and perfect lamp bulb structure may promptly be substituted for the impaired lamp to avoid total and dangerous extinguishment of the light signal. In most incandescent lamp signals two separate lamps are used behind one lens structure and light-up simultaneously, and if one lamp burns out the other lamp temporarily remains operative, but it is evident that two independent lamps may not be placed so as to sustain the incandescent filaments of both lamps substantially at or about the focal center of the lens, and therefore the lighting effect of their combined filaments is far less satisfactory and eflicient than that of the hereinabove described single lamp having duplex or plural filament portions both of which may be and are disposed substantially at or about the focal center of the lens structure.

Although I have particularly described the construction of one physical embodiment of my invention, and explained the operation and principle thereof; nevertheless, I desire to have it understood that'the form selected is merely illustrative, but does not exhaust the possible physical embodiments of the idea of means underlying my invention.

lVhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. An incandescent lamp signal comprising a casing, a lens sustained thereby, and an incandescent light source in the casing behind the lens and having duplex or plural filament portions normally in the same lighting circuit, both lying in substantially the same general horizontal plane, one filament portion having a greater resistance than the other and both disposed symmetrically about a point at substantially the focal center of the lens.

2. An incandescent lamp signal comprising a casing, a lens sustained thereby, and an incandescent light source in the casing behind the lens and having duplex or plural filament portions normally in the same lighting circuit, one filament portion having a greater resistance than the other and both disposed symmetrically about a point.at substantially the focal center of the lens.

3. An incandescent lamp signal comprising a casing, a lens, an incandescent lamp in the casing behind the lens having a single base and two lead-in wires, tWo plural convoluted filaments connected in multiple with said lead-in wires, said filaments being of greatly different resistance so as to have dif ferent life and being, both disposed symmetrically about a point constituting the focal center of the lens.

ELI BURTON PARSONS. 

